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2024 Vet physiology > Exam 1: Lecture 10: Cardiac and Smooth Muscle Physiology > Flashcards

Exam 1: Lecture 10: Cardiac and Smooth Muscle Physiology Flashcards

1
Q

what type of muscles are striated and involuntary

A

Cardiac muscle

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2
Q

What muscle is defined as a rhythmic beating due to built in pacemaker

A

Cardiac muscle

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3
Q

defined electrical syncytium of cardiac muscles

A

all cardiac cells contract the heart and this happens synchronsously

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4
Q

Cardiac muscle cells are connceted by _______ ______, which have mechanical juntions and eletrical connections

A

intercalated disks

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5
Q

what makes up mechanical junctions of cardiac muscle intercalated disks

A

fascia adherens and desmoses
- here to keep the cells from pulling apart

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6
Q

What makes up electrical junctions of cardiac muscles intercalated disks

A

gap junctions
- how the signal is passing so quickly

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7
Q

what organ acts as a pacemaker of the body

A

heart

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8
Q

AP of the heart initated in what node that is located in the right atrium

A

sinoatrial node

  • undergoes spontaneous depolarization
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9
Q

Where is AP propagated in the heart

A

between atrial cells and tracts
- forced through gap junctions

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10
Q

Once the AP propagated between atrial cells and tracts what happens next

A

it moves through atrial ventricular nodes

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11
Q

After traveling through the atrial ventricular node the charge moves to what portion of the heart?

A

bundles of His

Purkinje system

gap junctions of ventricular cells

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12
Q

AP passes through the entire heart within ______ msec and a contraction lasts ______msec

A

220

300

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13
Q

what is essential for contraction of cardiac muscle

A

extracellular calcium

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14
Q

Extracellular calcium enters the cardiac cells via what channels?

A

L type Ca channels

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15
Q

Once extrcellular Ca enters the cardiac cells with the L type Ca channels this causes a ________ of the AP - calcium is called “trigger Ca”

A

plateau

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16
Q

what is the role of trigger Ca

A

induce the release of Ca from the SR (ryanodine receptors)

  • NOT to promote acting myosin interaction
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17
Q

How much Ca will be released from the SR?

A

depends on the amount previously stored and the size of inward Ca current (trigger Ca)

  • more Ca2+ the stronger the heart contractions
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18
Q

For a contraction to occur we need _________ calcium to rise - being released from the SR

A

intracellular Ca

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19
Q

This process happens in cardiac cells, but not in what muscle cells?

  • Ca enters the cell during plateau causing Ca induced C release from the SR
A

Skeletal muscle

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20
Q

Is reaccumulation of Ca by the SR via the SR pump (SERCA) enough to cause relaxation?

A

NO

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21
Q

Because of extracellular Ca (trigger Ca) we need an additional method for relaxation, what is it?

A

Sarcolemmal 3 Na+ / 1 Ca2+ antiporter

and

Sarcolemmal Ca2+ pump (Ca2+ ATPase pump)

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22
Q

Can you increase the force of contraction in cardiac cells by recruiting more muscle fibers or by inducing tetany?

A

NO

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23
Q

How do you increase the cardiac muscle and force of contraction?

A

Modulate L type Ca channels during an AP

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24
Q

Extrinsic control of cardiac muscle contraction can increase force and rate of contraction via what system?

A

sympathetic nervous system

25
Q

which neurotransmitters of the SNS can help with increasing force of contraction of cardiac cells?

A

Epinephrine and norepinephrine

26
Q

Epi and NE bind to what receptors on the cardiac cell to increase force of contractions

A

B1 adrenergic receptors

27
Q

Once Epi and NE bind to B1 adrenergic receptors what system increases cyclic AMP

A

Adenlyly cyclase

28
Q

Adenlyly cyclase increases cyclic AMP, which phosphorylate L type Ca channels and _________

A

phospholamban

  • increasing activity of the SERCA pump: takes up Ca from cytosol and stores it. Able to dump more during next contraction
  • both of these help increase the total amount of Ca in the cyto
  • Positive ionotropic effect
29
Q

both of these help increase the total amount of Ca in the cytosol when phosphorylated

A

L type Ca channels

Phosophlamban

30
Q

Extrinsic control of contraction starts with what neurotransmitter?

A

ACh

31
Q

what does ACh bind to to control contraction of cardiac muscle

A

Muscarinic receptors coupled to G protein (inhibitory)

Adenylyl cyclase

32
Q

Once ACh bind to Muscarinic receptors coupled to G protein (inhibitory) and Adenylyl cyclase contractility is decreased due to ACh decreasing inward ______ flow and amount of ______ released from the SR

A

Ca for both answers

  • negative ionotropic effect
33
Q

what type of smooth muscle has wave like contractions such as peristalsis (help moves things along) and gap junctions

A

Single unit smooth muscle (unitary)

34
Q

what type of smooth muscle is modulated by hormones or neurotransmitters and acts independently of the muscles around it?

A

Multi-unit smooth muscle

35
Q

instead of sarcomeres what does smooth muscle have

A

dense bodies

36
Q

what is the purpose of dense bodies on smooth muscle

A

actin extends between dense bodies and myosin is located centrally

37
Q

instead of T tubules, what do smooth muscle have that act like T tubles and invaginations of sacromlema?

A

Cavolae

38
Q

instead of troponin in smooth muscle to block myosin binding sites, what do they use?

A

thick filament regulation

39
Q

depolarization that may or may not cause an AP = opens voltage gated Ca channels and hormones or neurotramsmitters = open ligand gated Ca channels

both cause Ca induced. Where is Ca released from?

A

SR

40
Q

the following are responsible for what action of smooth muscle?

  • depolarization that may or may not cause an AP = opens voltage gated Ca channels
  • hormones or neurotramsmitters = open ligand gated Ca channels
  • hormones or neurotransmitters = cause Ca release from SR via IP3
A

smooth muscle contraction

41
Q

As intracellular Ca increase what does Ca bind in smooth muscle

A

Calmodulin

42
Q

Calmodulin can bind how many Ca ions

A

4

43
Q

Ca-Calmodulin complex in smooth muscle activates what system?

A

myosin-light-chain kinase

44
Q

In smooth muscle what is the composition of myosin?

A

two heavy chains and two light chains

45
Q

what is thick filament regulation in smooth muscle when one light chain inhibits binding of myosin to actin

A

myosin light chain kinase (MLCK) phosphorylates the light chain and changes myosin head conformation

  • myosin head can now bind to actin
46
Q

During relaxation of smooth muscle , inhibition of Ca channels, inhibition of IP3 production and _________ _____

A

myosin phosphatase

47
Q

what is the job of myosin phosphatase

A

dephosphorylates myosin light chain

48
Q

What pump(s) are needed for relaxation of smooth muscle and the increase in Ca

A

Sarcolemmal 3 Na+ . 1 Ca2+ antiporter

and

Sarcolemmal Ca2+ pump (Ca2+ ATPase pump)

49
Q

________ relaxes smooth muscle by inhibition of MLCK even when intracellular Ca is high

A

cAMP

50
Q

cAMP relaxes smooth muscle by inhibition of MLCK even when intracellular Ca is high can treat what disease

A

Asthma

51
Q

_______ dependent activation of a myosin phosphatase
- nitric oxide-dependent increases of ____ will relax vascular smooth muscle and increase blood flow?

A

cGMP for both answers

52
Q

What are the types of smooth muscle tone

A
  • phasic smooth muscle
  • tonic smooth muscle
53
Q

What is phasic smooth muscle used for?

A

good for the GI tract
- rhythmic contractions

54
Q

What is tonic contractions used for?

A

Maintains tension for long periods (slow and sustained contraction) by the latch state
- myosin stays attached to actin for longer periods instead of dissociating immediately

55
Q

To maintain latch state does it require as much ATP?

A

NO

56
Q

Why is latch state important?

A
  • prolongs rigor without using much ATP
  • allows vascular smooth muscle to maintain tone and force for long periods of time - sustain blood pressure
57
Q

What occurs via dephosphorylation of myosin while still attached to actin?

A

latch state

58
Q
A

2024 Vet physiology (74 decks)

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